[YAML] fix output incorrect format for block scalar string

[HerrCai0907]

After outputting block scalar string, the indent will be wrong.
This patch fixes Padding after block scalar string to ensure the correct format of yaml.

The new added ut will fail in main.

@@ -3,4 +3,4 @@
     Just a block
     scalar doc
-scalar:          a
+  scalar:          a
 ...\n

[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Congcong Cai (HerrCai0907)

Changes

After outputting block scalar string, the indent will be wrong.
This patch fixes Padding after block scalar string to ensure the correct format of yaml.

The new added ut will fail in main.

@@ -3,4 +3,4 @@
     Just a block
     scalar doc
-scalar:          a
+  scalar:          a
 ...\n

---

Full diff: https://github.com/llvm/llvm-project/pull/131694.diff

2 Files Affected:

• (modified) llvm/lib/Support/YAMLTraits.cpp (+2-2)
• (modified) llvm/unittests/Support/YAMLIOTest.cpp (+30)

diff --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
index 28642e004c4f4..035828b594e84 100644
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -725,18 +725,18 @@ void Output::blockScalarString(StringRef &S) {
   if (!StateStack.empty())
     newLineCheck();
   output(" |");
-  outputNewLine();
 
   unsigned Indent = StateStack.empty() ? 1 : StateStack.size();
 
   auto Buffer = MemoryBuffer::getMemBuffer(S, "", false);
   for (line_iterator Lines(*Buffer, false); !Lines.is_at_end(); ++Lines) {
+    outputNewLine();
     for (unsigned I = 0; I < Indent; ++I) {
       output("  ");
     }
     output(*Lines);
-    outputNewLine();
   }
+  outputUpToEndOfLine("");
 }
 
 void Output::scalarTag(std::string &Tag) {
diff --git a/llvm/unittests/Support/YAMLIOTest.cpp b/llvm/unittests/Support/YAMLIOTest.cpp
index c0e9c57a77f19..d3e181075737d 100644
--- a/llvm/unittests/Support/YAMLIOTest.cpp
+++ b/llvm/unittests/Support/YAMLIOTest.cpp
@@ -1273,6 +1273,36 @@ TEST(YAMLIO, TestReadWriteBlockScalarValue) {
   }
 }
 
+struct V {
+  MultilineStringType doc;
+  std::string str;
+};
+template <> struct MappingTraits<V> {
+  static void mapping(IO &io, V &v) {
+    io.mapRequired("block_scalac", v.doc);
+    io.mapRequired("scalar", v.str);
+  }
+};
+template <> struct llvm::yaml::SequenceElementTraits<V> {
+  static const bool flow = false;
+};
+TEST(YAMLIO, TestScalarAfterBlockScalar) {
+  std::vector<V> v{V{}};
+  v[0].doc.str = "Just a block\nscalar doc";
+  v[0].str = "a";
+  std::string output;
+  llvm::raw_string_ostream ostr(output);
+  Output yout(ostr);
+  yout << v;
+  EXPECT_EQ(output, R"(---
+- block_scalac:     |
+    Just a block
+    scalar doc
+  scalar:          a
+...
+)");
+}
+
 //===----------------------------------------------------------------------===//
 //  Test flow sequences
 //===----------------------------------------------------------------------===//

[thurstond]

I'd suggest precommitting TestScalarAfterBlockScalar (with EXPECT_EQ changed to the current, erroneous output) as a separate patch, and then rebasing this patch on top of that; that would make it clearer what your fix accomplishes.

[HerrCai0907]

ping @thurstond

[arsenm]

can you rebase to retrigger tests